Premium
Corrosion behavior of Ni‐Cr‐base commercial alloys in flowing Ar‐42.6%O 2 ‐14.7%Br 2 gas mixture at 700°C
Author(s) -
Lee S.,
Tsujikawa S.
Publication year - 1997
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.19970480704
Subject(s) - materials science , corrosion , metallurgy , inconel , nimonic , alloy , liquidus , scanning electron microscope , hydrogen , oxide , superalloy , chemistry , composite material , organic chemistry
Corrosion behavior of Ni‐Cr‐Base commercial alloys has been investigated in an argon‐42.6% oxygen‐14.7% bromine gas mixture at 700°C which was one of the environments encountered in the UT ‐3 thermochemical water decomposition reaction process to produce hydrogen. The test alloys were Inconel 600, Hastelloy C‐276, Inconel 625, and Nimonic 80A. Two‐dimensional thermodynamic phase stability diagrams were constructed for nickel, chromium, iron, tungsten, cobalt, titanium, and aluminium to predict the condensed corrosion products that are stable with respect to the representative alloying elements when the alloy is exposed to the argon‐42.6% oxygen‐14.7% bromine gas mixture at 700°C. The oxides were thermodynamically stable phases with respect to the corresponding metals. Post‐reaction treatment of test alloys included discontinuous mass‐change measurements, scanning electron microscopy (SEM), electron probe micro‐analysis (EPMA) for morphological and compositional investigation of the corrosion products, and the X‐ray diffraction (XRD) for phase identification. XRD identified oxides and spinels as corrosion products but low‐melting metal bromides were also detected for all alloys with deleterious effects on high‐temperature properties of these alloys during exposure to the environment. The poor corrosion resistance of Inconel 600 and Hastelloy C‐276 was mainly caused by the cracking and spalling of iron and nickel‐rich oxides and further growth of various metal bromides beneath the oxide scale following prolonged exposure. Inconel 625 and Nimonic 80A alloys performed better than Inconel 600 and Hastelloy C‐276, mainly because of their aluminium alloying element and lower iron content.